This is a mid-engine BEC topic.

Idea: Mate a bike engine directly to the input shaft of a FWD transaxle and place it transverse mid-ships like the Elise or MR2 (or Bala )

Question: Does everything rotate in the right direction?

I think the following is correct:
- Output shaft of Bike Engine - CounterClockwise
- Input Shaft of Transaxle (when seen from same direction as bike output) - CounterCockwise.

Is that right?


The main shifting is done with the sequential bike box but remove 1st, 2nd and 3rd gears from the transaxle to reduce weight. Leave reverse, 4th and 5th gears. Since the transaxle still has 4th and 5th, those can also be shifted via a secondary lever to offer two sets of on-the-fly gearing ratios. 4th on the transaxle would be for rapid off the line acceleration with lower top speed and 5th could be used for greater top end speed. Now you have 12 forward speeds plus 6 reverse speeds! All of this in a compact and lightweight (depending on choice) unit. I would get a FWD transaxle with LSD.
How to attach the motor to the transaxle? - Front engine BEC's use a simple bike sprocket-to-ujoint adapter right? So why not a bike sprocket to splined input shaft adapter?Balanced and perfectly centered to prevent it from vibrating, it could have a spigot bearing hole machined into the end to support the transaxles input shaft...

Is this a bad idea? Can you shoot holes in it?

A complete BEC mid-engine drivetrain in a simple and reliable package. I think it would be a fairly low cost and an effective way to make a mid engine BEC middy.

Graber

All do-able, Steve. I think there's a company in the UK called Allens, who use this approach. Perhaps some of our UK posters can confirm?
There are a couple of issues. Reverse is usually an idler gear in partnership with 1st, so you'd have to leave 1st in the box. You'd also need to shift the bike box into a high gear when reversing so that you weren't doing 9000rpm and only going 5 mph!

Someone on this forum is using one. There's also this version:
Rescued attachment transaxle 2.jpg

Add the weight of a gearbox to the weight of a car and put it all through a bike clutch and you are putting a strain on it that it isn't designed for. Also car gearboxes are designed for bigger torque outputs than a bike engine can supply. You will sap the hp just turning it over so the total bhp at the wheels will be down to car figures. The final drive ratio will also need some sorting and the mating of the two parts, bike engine output to gearbox input, will result in something about 4 feet tall. Let us know how you get on with it, sounds like a locost theory group one to me.

yours, Pete.

I think you may have some challenges. I don't think you could mate the gearbox housing very easily to the engine due to the layout. This would probably necessitate mounting them separately and using some form of cush drive to allow for any rotational misalignment. Without that you would need to get alignment within a few thou's at the most. Otherwise you will knock out input shaft bearings. All in all it would be a serious engineering project.

Then there is also the issue of final drive ratios as mentioned by Pete. Although this may be solvable.

From a weight perspective, I am not sure how much a stripped fwd gearbox would weigh. My powertec axle weights about 50 lbs including LSD.

The other options are the powertec axle shown above that I am using in my project. The downside to this is the cost and it has straight cut gears. These will be really noisy and I wouldn't like to use it for anything but a track car with very occasional road usage. Alternatively, you could go the Coram route and mount the engine longitudinally with a short prop shaft to say a BMW diff. This would be the cheapest. I am not sure if you have room or not.

Are you sure your car really suits bike engined power. They are noisy and the drive trains can be kind of clonky with a lot of backlash. So not the most ideal road setup. Really you don't want to be much over about 1100 lbs with a stock Busa if you want decent performance and reasonable clutch wear. Would your car be in that range?

Thanks LMP, that is a most helpful post.

Considering where the output shaft of most bike is, I think that it would be an almost perfect shot to mate them up. Getting the tolerances would certainly be a job for an experienced machinist. Not something I would attempt. However, the end result would be something like a flat bellhousing with no clutch or flywheel.

I'm sure that a transverse FWD transaxle weighs more than your powertec! However, it probably costs $1000 more than a car transaxle.

My car is probably over-built to be a mid-bec. It will weigh closer to 1500Lbs (with 4AGE engine) when finished.) I am looking ahead to some of my future projects.

I didn't know that the Coram LMP was longitudinal. How did they solve the reverse rotation engine issue with the differential from a standard rotation car?

Steve

Why not ask them...

http://www.coram-automotive.com/forum

I'm sure you'll find the guys most helpful!

Ian

[Edited on 12/8/03 by ijohnston99]

quote:

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How did they solve the reverse rotation engine issue with the differential from a standard rotation car?

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Ahaaa!! <sheepish grin> You are right.

I still have in my mind the Yamaha Vmax shaft drive engine that I was going to use. That one for sure rotated in reverse direction...

Thanks for pointing me straight. I'll be moving along now...

Graber

You'd only need to invert the diff' to solve the reverse rotation problem, anyway.

Just be sure to block the breather hole on the top before inverting, then create a new one on the... er... 'bottom' - which would then be the top... *ahem*

A lot of cars that use the Porsche transaxle (e.g. Ultima) do this.

I guess this means you'd still be able to use the VMAX engine?

Steve.